Stiebel Eltron LWZ & LWA
Controls Stiebel Eltron LWZ and LWA ventilation units via Modbus TCP gateway.
This template integrates Stiebel Eltron LWZ and LWA ventilation units via Modbus TCP through the ISG gateway. It reads temperatures, operating status, and fault codes, and allows control of operating modes, fan stages, and DHW setpoints.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 23, read and write
- Brand
- Stiebel Eltron
- Key readings
- Outside Temperature · Flow Temperature · Return Temperature · Actual DHW Temperature · Actual Room Temp HC1/HC2 · Operating/Fault/Bus Status
- Available commands
- Operating Mode · Room Temperature Day/Night · DHW Set Day/Night · Fan Stages (Day/Night/Party/Manual)
- Compatible models
- LWZ · LWA
- Last updated
Registers (23)
23 read, 11 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| 1 - ACTUAL ROOM T HC1 | °C | Read | |||
| 4 - ACTUAL ROOM T HC2 | °C | Read | |||
| 7 - OUTSIDE TEMPERATURE | °C | Read | |||
| 8 - ACTUAL VALUE HC1 | °C | Read | |||
| 12 - FLOW TEMPERATURE | °C | Read | |||
| 13 - RETURN TEMPERATURE | °C | Read | |||
| 16 - ACTUAL DHW TEMPERATURE | °C | Read | |||
| 1001 - OPERATING MODE | Read and write | ||||
| 1002 - ROOM TEMPERATURE DAY | °C | Read and write | |||
| 1003 - ROOM TEMP. NIGHT | °C | Read and write | |||
| 1005 - ROOM TEMPERATURE DAY | °C | Read and write | |||
| 1006 - ROOM TEMP. NIGHT | °C | Read and write | |||
| 1012 - DHW SET DAY | °C | Read and write | |||
| 1013 - DHW SET NIGHT | °C | Read and write | |||
| 1018 - DAY STAGE | Read and write | ||||
| 1019 - NIGHT STAGE | Read and write | ||||
| 1020 - PARTY STAGE | Read and write | ||||
| 1021 - MANUAL STAGE | Read and write | ||||
| 2001 - OPERATING STATUS | Read | ||||
| 2002 - FAULT STATUS | Read | ||||
| 2003 - BUS-STATUS | Read | ||||
| 2004 - DEFROST INITIATED | Read | ||||
| 2005 - OPERATING STATUS-2 | Read |
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Use cases
- Monitor outside, flow, and return temperatures on a live dashboard to verify ventilation system performance.
- Set room temperature and DHW setpoints remotely to adjust comfort levels without a site visit.
- Create an alert when a fault status register changes to detect ventilation failures early.
- Switch fan stages between day, night, party, and manual modes based on occupancy schedules.
- Track actual DHW temperature over time to verify hot water performance and identify efficiency drops.
- Compare HC1 and HC2 room temperatures to detect imbalances between heating circuits.
Installation
Install and configure the Stiebel Eltron ISG gateway according to the manufacturer instructions and connect it to the same local network as your ModbusCloud gateway.
Assign a static IP address to the ISG gateway and note the Modbus TCP port (default 502).
Connect your ModbusCloud Gateway to the same network and ensure it can reach the ISG gateway IP address.
Import the Stiebel Eltron LWZ and LWA template from the ModbusCloud template library into your project.
Configure the connection in ModbusCloud by entering the ISG gateway IP address and port, and verify that register addresses use zero-based indexing.
Commission the template by checking live readings for outside temperature and operating status to confirm communication is working.
Things to watch for
Why are all temperature values showing as very large numbers?
Temperature registers use uint16 encoding with a scale factor. Verify that the template scaling is applied correctly. The outside temperature register is an exception and uses int16 encoding to support negative values.
Why does my ModbusCloud gateway not connect to the ISG?
Confirm that the ISG gateway and the ModbusCloud gateway are on the same network or have a routed path between them. Check that the ISG IP address and Modbus TCP port (default 502) are correctly entered in the template configuration.
Why do register addresses seem off by one compared to the Stiebel Eltron documentation?
This template uses zero-based addressing. A register documented as 1001 in the Stiebel Eltron manual corresponds to Modbus address 1000. Ensure your configuration does not add an additional offset.
Do I need a specific ISG firmware version for all registers to work?
Yes. Older ISG firmware may not expose all registers used in this template. Update the ISG to the latest firmware version available from Stiebel Eltron before commissioning.
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